1. Field of the Invention
The present invention relates to a switch used in a flip-type or folder-type radio terminal, and in particular to a hall switch which has an adjustable sensing value.
2. Description of the Related Art
In general, in a foldable terminal for mobile communication, the terminal is controlled by sensing opening and closing of a flip or folder to enable a speech path or activate a display lamp. In other words, the speech path is enabled when a user opens the flip of the terminal to answer a call, and the speech path is disabled by closing of the flip. Also, the display lamp is activated by opening the flip so that the user can see the display. Hereinafter, the xe2x80x9cfoldable terminalxe2x80x9d will be referred to as a terminal comprised of first and second structures such as a flip-type or folder-type radio terminal for mobile communication.
In the prior art, a lead switch comprised of a permanent magnet and an elastic magnetic body has been used to sense the opening/closing of the flip. For example, when the flip is closed, the magnet approaches the magnetic body so that the magnetic body closes a contact. When the magnet withdraws from the magnetic body, the magnetic body opens the contact.
However, there is a problem that since the foregoing lead switch is a mechanical structure, the distance between the magnet and the magnetic body is required to be the same in order to maintain uniform strength of each model. For example, an erroneous operation can take place when the switch does not close the contact in a new model because the distance between the magnet and the magnetic body is too long. Therefore, in the new model, the strength of the magnet, or the distance between the magnet and the magnetic body must be adjusted.
It is therefore an object of the invention to provide an apparatus for adjusting the sensitivity of a hall switch of a folder-type or flip-type radio terminal without replacing a magnet or adjusting the distance between the magnet and a magnet body even in a new or different model.
Accordingly, a switch for sensing an open or closed state of a foldable terminal which has first and second structures rotatably joined to each other is provided. The switch includes a hall sensor for generating voltage according to the strength of an input magnetic field proportionally to the distance to a magnet; a variable amplifier for variably amplifying the voltage from the hall sensor to output a variably amplified voltage signal in response to a control signal; and a comparator for comparing the signal from the variable amplifier with a reference voltage to output a signal for indicating the open or closed state.